


Dearly Beloved

by witchofstars



Category: Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: Anal Fingering, Anal Sex, Birthday Sex, Blow Jobs, Bottom Seteth, Dom/sub, Dom/sub Undertones, F/M, Female My Unit | Byleth, Food Sex, Icing, Light Bondage, Nipple Play, Oral Sex, Praise Kink, Seteth Gets Pegged That's The Story, Strap-Ons, Teasing, Vaginal Sex, top byleth
Language: English
Status: Completed
Published: 2019-08-18
Updated: 2019-08-18
Packaged: 2020-09-06 23:21:50
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,205
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/20299618
Author URL: https://archiveofourown.org/users/witchofstars/pseuds/witchofstars
Summary: "I need you." Byleth whispered against his lips, delicate hands snaking their way through Seteth's green locks. She relished in these moments when she had him all to herself. Byleth could close her eyes and imagine, if only for a few seconds, that they were the only two beings in the world."In which it's Seteth's birthday and Byleth treats him with a special surprise.





	Dearly Beloved

Seteth finds himself working long hours in his private study most days, well past his scheduled meetings with Rhea and other church officials that visit the monastery. There is always work that needs to be done, important letters to write, seminars to plan out, work that could be done, more that he should be doing--

Seteth's train of thought was disrupted by several loud knocks on his door. He whipped his head up from the mountain of papers his nose was buried in.

Seteth cleared his throat. "It's open, you can come inside." Few would dare to knock on his door so late at night, so he wasn't surprised to see Byleth emerge from the other side of the door. What did surprise him was the silver platter of tea and cake in her hands.

"I just knew I would find you here," Byleth said with a smirk tugging at the corner of her mouth.

"Byleth, what brings you here with tea at this hour?" Seteth questioned, adjusting his silver reading glasses before crossing his arms.

Byleth chuckled. Seteth's cheeks turned red underneath the sterling frames. "Why Seteth, have you truly forgotten your own birthday?" 

Seteth shook his head. "As if Flayn and the Archbishop would allow me to forget... no, they had brought me gifts earlier in the day but it is really just another ordinary day for me. I do not have the time to spare for such frivolities when there is work to be done."

Byleth nodded, her face returning to its usual stoic expression. "I understand. Well then, I can leave you to your work if that is what you desire-"

Seteth quickly made a move to cut off the professor before she could make a move to exit his study. "I never said I would not accept this gesture, Byleth."

"Oh?"

"Forgive me, I did not mean to sound ungrateful. I truly do appreciate the thought... and perhaps it is time that I pause my work for the evening." Seteth dipped the quill pen he was holding into the pot of ink on his desk, then moved some stacks of parchment to the side so that Byleth could set the platter down.

"I'm glad we could come to an understanding, then." Byleth replied, the grin slowly returning to her face. As she walked back over to the desk, Seteth caught a brief glimpse of moonlight glimmer in her deep blue eyes that further complimented her smile. If he could do anything to keep that radiant smile on her face, he would gladly oblige no matter the request.

When she set the platter down in front of him, Seteth was able to get a better look at the its contents: A small cake laden with strawberries and topped with a white buttercream icing, cut into the shape of a heart. Next to the cake were two pairs of cutlery, tea cups, and a silver kettle filled with his favorite tea. Seteth gazed in awe between the cake and Byleth and murmured, "You... prepared my favorite cake and tea yourself?"

Byleth shook her head. "I had a little help from my students. Mercedes is a skilled baker; I simply followed her instructions." She turned her gaze away from him, sheepishly eyeing the hardwood floor. "Do you... like it? It's not much, but you have been working so hard and I thought it would be best to do something-"

Byleth was cut off by Seteth suddenly bolting up from his desk, inadvertently making the teacups rattle. "Do I like it? Byleth, I love this," he assured her, stepping away from his chair to approach Byleth and wrap her in a tender embrace. Her dark blue hair smelled of fresh strawberries and cream, it was heavenly. "You did not have to go to such arduous lengths for me, you have quite the busy schedule yourself and yet you went out of your way, as you always do."

It was Byleth's turn to be caught off guard by the sudden display of affection. "Maybe it's not as... selfless as I make it appear," she replied, rubbing the small of his back.

"What do you mean by that?"

"I really wanted to see you. I have barely had a moment alone with you all week." Byleth pulled away slightly so she could admire Seteth's face, illuminated by the gentle streams of pale moonlight that shone through the window behind them. His deep green eyes which were piercing and harsh towards her only months ago had now gazed upon her in pure adoration. She could hardly believe there was ever a time when he viewed her as a nothing more than a threat to the Archbishop.

"I need you." Byleth whispered against his lips, delicate hands snaking their way through Seteth's green locks. She relished in these moments when she had him all to herself. Byleth could close her eyes and imagine, if only for a few seconds, that they were the only two beings in the world.

Seteth's breathing grew shorter, the blush on his face deepening when his partner uttered those words. She was so impossibly close he could practically taste the notes of strawberries and vanilla on her breath, and he craved nothing more than to taste it on his lips. "It is my pleasure to oblige you, my beloved." Byleth let out the softest noise as Seteth closed the distance with his lips, smiling into the tender kiss.

He pulled back just as Byleth leaned closer to deepen the kiss, saying, "However... I was looking forward to having a little taste of this cake first. It is quite delicious and I would hate to let it spoil overnight."

"Maybe we don't have to let it go to waste." Byleth said with a coy smirk on her face, keeping one arm slung around the man's waist while reaching over to scoop a dollop of icing off of the cake. Seteth raised an eyebrow in confusion but he soon realized what his lover was trying to get at when she slowly sucked the icing off her finger, looking up at him as she dipped her own finger deeper into her mouth before pulling it back out again. Such a tantalizing, lewd sight, and the thought of replacing her finger with his own cock made him moan on the spot.

"Oh," he panted, feeling the last of his composure start to slip from his grasp. Byleth leaned back in to kiss her lover once more, this time making sure he could taste the sweet buttercream icing on her tongue.

Seteth felt Byleth pressing him back against his desk, causing several stacks of papers to shift and flutter to the ground. He was usually very particular about keeping his belongings in order, but tonight a little mess was the furthest thing from his mind. He tilted his head to the side to deepen the kiss, their tongues sliding together as they pulled each other as close as they possibly could, not wanting to let the other go fro even a moment. Byleth ground her hips against the man, moaning into his mouth as she felt him tenting beneath the fabric of his trousers.

Having playful, needy trysts in Seteth's office was not an uncommon event. It was rather thrilling to both parties, but tonight Byleth wanted to treat her lover to something a little more intimate, and the office was unfortunately not the most ideal place. "Come, let us take this to bed," she murmured, breaking the kiss to pick up the cake. The tea would have to be left behind for another day.

"This was your plan all along, was it not?" Seteth chuckled, smoothing back flyaway strands of hair from Byleth's face before kissing her forehead. "You truly are a master tactician... very well, I could not agree more."

Byleth's smirk melted into an ecstatic grin. The sound of Seteth's laugh made her dizzy with adoration; no one else ever got to see this side of him. It was reserved for her alone to savor, his soft lips were meant for her to claim. He was hers and hers alone.

________

The pair stumbled into Seteth's room several minutes later, both of their jackets practically hanging off their bodies. Seteth made sure to lock the door shut while Byleth hurriedly set the cake down on the nightstand before reuniting in a fiery kiss. Seteth pushed Byleth's cloak off her shoulders and onto the ground, and she did the same for him; they rushed to get each other out of their clothing, craving the warmth of each other's bare skin.

Byleth's peachy skin was littered with faded scars from her days as a mercenary. So much about her was a mystery, but her hidden scars revealed stories of countless hard-fought battles and close calls. "Amazing," Seteth whispered as he trailed kisses from the side of her neck down to the scars on her shoulder blade. "You are so beautiful, beloved."

Byleth shivered under his touch. She felt his hands undo the clasps that kept her top together and let it flutter to the ground, revealing her black lace bra. She helped him slide out of his robes and caressed his toned, muscular body. Unlike her, Seteth's skin was free of scars and callouses, smooth as silk to the touch. The pair quickly freed themselves of the rest of their clothes, removing any barrier of fabric that was left so there was nothing left between them.

Byleth dipped her fingertips into the cake and scooped out some more icing, catching little slices of strawberry. She laid herself down onto Seteth's bed and delicately placed the icing on her breasts, playfully teasing her nipples for the man standing above her. Seteth made a move to bend down to kiss her but she nudged his legs back with her foot. "Ah ah, I'm not done yet. I want you to watch me." She said, somehow able to keep a straight face while she continued to massage her breasts and place the strawberry slices on top of her nipples. From where she was positioned on the bed, she was still able to easily reach over to the nightstand and swipe some more icing off the cake, strategically placing it down her stomach and thighs. Seteth wanted to protest but knew better, so he bit his lip and watched Byleth put on a show for him. He yearned to pleasure himself as he watched Byleth tease her clit with an icing-covered fingertip but he knew better than to act outside of her orders.

The soft noises that escaped her lips made his dick twitch. "B-beloved, please, allow me to touch you," he begged, bringing his hand up to his mouth to bite down on his fingertip and suppress his moans. Normally he loved to watch Byleth masturbate in front of him, but he was growing impatient with the desire to pleasure her himself.

"Tell me what you wish to do to me and perhaps I will permit it," she teased, her playful chuckle turning into a moan as she slid her finger inside of her wet pussy and fucked herself in front of him.

"I-I wish... to pleasure you, to place myself between your thighs and eat you out," Seteth groaned, biting hard enough on his finger to leave marks. "I wish to be good for you, my love. Please, I want to make you cum and taste it on my lips."

Byleth moaned in response, the sound of her beloved professor voicing such dirty thoughts made her even more wet for him. She nodded and said, "Come, you may touch me now."

Seteth sighed in relief, and before Byleth could blink he was already on top of her, pulling her finger out of her entrance while kissing her deeply, sliding his tongue in sync with her own. His large cock dragged against her clit and she moaned into his mouth, relishing the sensation.j

Seteth once again kissed down Byleth's neck, this time sucking lightly on the sensitive skin until it left small bruises. He left more marks around her clavicle, and when he trailed his way down to her breasts he slowly swirled his tongue around her left nipple, licking up the icing. It was delicious and he had no doubt the cake itself tasted just as good, but this was far better.

"Yes, that's it," Byleth breathed, "You're so good, Seteth." She smiled down at him and stroked his hair with one hand, the other caressing his toned back. The man buckled under the praise, the vibrations from his moans going straight to Byleth's core. She gently pushed his head forward, making him take her nipple into his mouth and eat the icing and strawberry on top. Seteth happily took it in, sucking the perky bud once he swallowed the sweet buttercream. Byleth eased her grip on his head so he could move to her other nipple, repeating the teasing motions with his tongue before lapping up the icing and sucking the bud, flicking the abandoned one with his index finger.

Byleth pulled him off with her hand so she could kiss him again, tasting the buttercream on his tongue. "Such a good boy," she murmured breathlessly. "I love you so much."

"Nothing makes me happier than to hear you say that," Seteth breathed back, his cheeks burning deep red. The praise melted away his stress from his busy week, and he emptied his mind of everything except for Byleth. He scoot a little further down so he could lap up the icing on her stomach, dragging his tongue down to her inner thighs. His facial hair tickled her, making her giggle and reflexively grip his hair tighter. He flashed her a devious grin and rubbed his face into her thigh, making her laugh louder.

"Stop that!" She cried, smiling warmly at him. Her authoritative demeanor melted for just a moment, and she sat up so she could bend down and kiss the top of his head. He only revealed his playful side around her, and it was so endearing it always made her cheeks turn a deep shade of peachy pink. Seteth nuzzled her lovingly, then used his hands to spread her legs apart. Her entrance leaked with precum that pooled onto the sheets. He positioned his face between her thighs and gazed up at her with half-lidded eyes, patiently awaiting her orders.

Byleth nodded, giving him the signal to lav at her folds with his tongue. She laid back down, propping herself up with the mountain of plush pillows on Seteth's bed so she could still get a good look at him eating her out. She was quiet during sex, her noises rarely louder than a whisper, but Seteth didn't mind at all-in fact, he preferred it. He found enjoyment in her actions which were far more indicative of how pleased she was; the way she tugged on his hair whenever he teased her clit with his experienced tongue, how she let out a particularly shaky moan when he sucked lightly on her folds. When he dipped his tongue into her entrance her breathing grew more labored, and she screwed her eyes shut as she tightened her grip on his long hair. "M-more," she gasped, "don't tease me."

Seteth dutifully obliged, thrusting his tongue deeper inside of her. He set a fast, brutal pace, taking a hand off her leg to massage her clit while he fucked her with his tongue. Her eyes fluttered open and she caught him staring up at her, his eyes filled with admiration and lust. She came with a faint whimper of her beloved's name, her pussy pulsating around Seteth's mouth. He slid his tongue out of her entrance and eagerly lapped up her cum, murmuring gentle praises deep into her skin.

His cock had been neglected the entire time, but he willed himself not to pleasure himself unless his beloved allowed it. Byleth cupped his face in her hands and brought him up for a kiss, tasting her cum and a hint of strawberry in his mouth. "I think you deserve a reward for being so good for me." She praised him, smoothing back his hair. "Would you like to fuck me? Or perhaps you wish to be filled tonight instead?"

"I-I..." Seteth trailed off and tried to hide his face in Byleth's hand, flushing impossibly red. "Yes... I want you inside of me."

"What was that?" Byleth teased. "Speak up, my love."

Seteth cleared his throat, still having trouble meeting her eyes as he spoke louder. "I want you to fuck me, Professor... p-please."

Byleth kissed the corner of his mouth, satisfied with his answer. "If that is the reward you seek, I will gladly give it to you. You have earned it," Byleth cooed. She sat upright and swapped places with Seteth, pinning him to the bed. She opened his nightstand drawer and pulled out two long silk ribbons which she used to tie his hands above his head and to the bed posts. He tugged his wrists against the restraints to make sure they were secure and flushed when they didn't give way. He loved the feeling of being tied down, completely at the mercy of his beloved professor to use him as she pleased.

Byleth wasted no time in getting to work, burying herself between Seteth's legs to lick her way up the thick base of his cock. It took all of his concentration to keep himself from bucking up into her touch, moaning in relief from finally being stimulated. She wrapped her lips around the swollen head and sucked down as far as she could go, sliding more than half his length down her throat before sliding out with a wet pop. She bobbed her head back and forth, pressing her hands down on his thick thighs to keep him from fucking up into her mouth. Her pace was slow, teasing, and the feeling of his cock dragging in and out of that wet heat made Seteth bite his lip hard enough to draw a prick of blood.

"Byl-... Professor," he pleaded, "Please, I need more." Not being able to pleasure himself was torture in the best possible way; to be reduced to a begging, pleading mess because of her, to relinquish his control, felt so sinful and so freeing.

Byleth pulled her lips off his cock once more and rummaged through the drawer for a bottle of oil. She opened the cap and let some oil drip onto her fingers, then set the bottle down and spread the oil around her partner's hole while using her free hand to stroke his cock. The next thing he knew her finger had slipped past the tight ring of muscle, soon followed by a second one.

"Ah!" Seteth gasped, writhing beneath Byleth. His groans grew louder and needier as she silently plowed him with her fingers, the brief moment of pain dissipating into searing pleasure. He rocked his hips up in time with her thrusts which made her move faster, and after several minutes of this she added a third finger inside his ass. His eyes rolled back into his head as he cried out, "More, please, professor..." over and over. He could feel his orgasm building up deep inside of him, and he knew he wasn't going to last much longer.

As if sensing it, Byleth pulled her fingers out just as he was nearing his peak. He groaned loudly, shaking from the feeling of sudden emptiness. Byleth got off the bed and knelt down so she could pull out a black box stored underneath it, which contained a variety of toys, restraints and gags inside. Perhaps they would make use of some of those items another day, but for now all she needed was her favorite toy: A long and thick pink dildo that was ribbed along the tip and was fastened to a black leather belt. Byleth secured the belt to herself and returned to her lover, who moaned when she positioned herself on top of him and coated his entrance and the dildo with oil.

She entered Seteth without warning and slowly pushed forward until the entire length was buried inside of him, right up to the hilt. "Fuck…" he cursed, the feeling of being filled up was so overwhelming it brought tears to his eyes. Byleth kissed them away tenderly, halting her movements so that her lover could adjust to the toy.

"Are you alright?" She asked. She grew concerned by his expression, his lip bleeding more as he unconsciously bit harder. When he didn't reply she spoke up, saying firmly, "Seteth, talk to me. If it hurts I can pull out-"

"N-no!" Seteth begged, snapping out of his haze when he heard her voice and tasted copper on his tongue. "My apologies, I do not know what came over me. It feels so good, do not leave me empty. I want this more than anything. Don't be gentle with me, I can take it."

"Are you sure?" Byleth asked, raising an eyebrow. "Tell me our safe word for when it becomes too much and you need me to stop."

"Wyvern," Seteth recalled. Neither one of them have had to use the safe word before, but it was important to have regardless. "I will be okay, my beloved. Now please, take me."

"With pleasure." Byleth pulled nearly the entire length of her cock out, the ribbed edges dragging against the flare of Seteth's hole. He moaned in protest, which was quickly stifled when she slammed back into him. She fucked him into the mattress, setting a punishing pace. Seteth's cries carried into the hallway, and a masochistic part of him hoped that somebody heard, so they knew exactly what they were doing and that the right hand of the Archbishop was being claimed by his cherished professor. He drooled onto one of the pillows, lost in a haze of pleasure and heat.

Byleth found his prostate and angled herself just right so that she hit it with each thrust. She slowed down so she could sit up and lift Seteth by his legs, spreading them further, then thrust her cock even deeper inside of him. "You take me so well," she panted, hitting that bundle of nerves once again.

"Professor!" Seteth cried, tears rolling down his cheeks. He cried out like a bitch in heat, rendered helpless by the restraints and forced to take whatever was given to him. Byleth knew just how to reduce him to such a state, to have him fall to her knees with a single command and beg for his release. Despite his cock being neglected he could feel himself reaching his peak again. "Professor, please… t-tell me that I am good."

"You are so good," Byleth replied, grunting as she could feel her own orgasm draw close. "Such a good boy. Come for me, darling."

Just like that, with a single command Seteth let himself go. He moaned as he came untouched, coating his stomach with thick ropes of cum. Byleth pulled out and quickly unfastened the strap, tossing it to the ground, then untied Seteth's wrists and seated herself on his oversensitive, throbbing cock, still leaking with cum. He sat up and held her close, fucking her through the rest of his orgasm and filling her cunt with his seed as she released at the same time.

"Seteth…" Byleth slumped against the man's chest, moaning his name like a prayer as she felt him fill her core. They stayed like that for a minute, completely winded from their sex and peppering each other's faces and necks with lazy kisses. Seteth used the last of his energy to slide out of her slowly, causing a small trail of cum to leak out of her entrance. He let himself fall back onto the bed, his own hole still twitching from being thoroughly fucked. Byleth beamed at him, placing a quick kiss to his forehead before leaving his side to retrieve a cloth from his closet to wipe themselves off, knowing how much Seteth hated to be sticky and sweaty after sex. Seteth was amazed that she still had the energy to clean up afterwards.

"Was that okay?" Byleth asked sheepishly, kissing dried-up streaks of tears away from Seteth's cheeks. "I did not hurt you, did I?"

"Not at all," Seteth chuckled, shaking his head. He brushed her bangs out of her face and kissed her softly, gazing upon her with so much love and adoration she thought her heart would burst. "Byleth, you are incredible. There is nothing I find more enjoyment in than our lovemaking. You are too good to me."

His soft words made her melt in his arms. "I love you," she whispered, kissing his bruised lips. "Happy birthday."

"Thank you, my darling. I love you too." Seteth murmured, smiling tenderly at his beloved partner as he pulled the blankets over their bodies and held her close to his chest. The comforting sound of his heartbeat lulled her to sleep, and Seteth kissed her forehead one more time before shutting his eyes as well.

**Author's Note:**

> Please be gentle with me, this is my first smut fic and also my first fic I've written in years but my deep love for this game and Seteth pulled me back into this hell. I am a beacon of sin. Let me know if you would like me to write more! I'm on twitter @AstralAtelier :)


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